In recent years, the development of ceramic matrix composites (CMC) as one type of fiber-reinforced composite material is being promoted. CMC is a composite material in which ceramic fiber is reinforced with a matrix, and is characterized in being light and having superior heat resistance properties. By leveraging these characteristics, for instance, the possibility of using CMC in aircraft engine parts is being considered, and the practical application thereof is currently being sought. Note that the use of CMC as aircraft engine parts is expected to considerably improve the fuel economy.
The general process of forming CMC is as follows. Foremost, roughly several hundred ceramic fibers are bundled to prepare a fiber bundle, and the prepared fiber bundles are woven into a fabric. As the weaving method of fiber bundles, for instance, known are methods referred to as three-dimensional weaving and plain weaving. Three-dimensional weaving is a method of weaving the fiber bundles from three directions (XYZ directions) to prepare a fabric, and plain weaving is a method of weaving the fiber bundles from two directions (XY directions) to prepare a fabric.
After the fabric is prepared, a matrix is formed via CVI (Chemical Vapor Infiltration) and PIP (Polymer Impregnation and Pyrolysis), and CMC is thereafter formed by ultimately performing machining and surface coating. Here, the orientation of the fiber bundles in the formed CMC will considerably affect the strength of that CMC.
In other words, if the fiber bundles are meandering at a location where they should actually form a straight line, generally deviating from the reference axis whether they should actually be positioned, or ruptured midway, the strength of CMC will considerably deteriorate. Meanwhile, when the fiber bundles are appropriately arranged in alignment in a specific direction without any meandering, deviation or rupture, CMC will yield high strength and superior heat resistance properties. Thus, in order to confirm whether the strength of the formed CMC is sufficient, it is important to evaluate the orientation of the fiber bundles.
PTL 1 discloses an orientation analysis method of binarizing a sliced image of a resin molding and acquiring a binary image, subjecting the acquired binary image to Fourier transformation to acquire a power spectrum image, and determining the main axial direction of an oval that is perpendicular to the oval drawn based on the acquired power spectrum image as the orientation of the filler (fibers) contained in the resin molding.
Moreover, NPL 1 discloses a technology of imaging a fabric produced by weaving fiber bundles using an X-ray CT device and acquiring an X-ray CT image, and performing a calculation using a special filter function with regard to the acquired X-ray CT image in order to analyze the orientation of each and every fiber configuring the fiber bundle.